Acoustic matching member, acoustic matching member group, and medical imaging apparatus

ABSTRACT

An acoustic matching member configured to be disposed between a breast placed on an imaging table and a compression plate disposed opposite to the imaging table is proposed. The acoustic matching member includes a protruding portion that protrudes toward the imaging table and that is provided in an end portion on a deepest side when viewed from a chest wall side of a subject in a case of compressing a breast of the subject in contact with the compression plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of, and claims priorityto, application Ser. No. 15/473,611, filed on Mar. 30, 2017, the entirecontents of which is incorporated herein by reference in its entirety.Further, this application claims priority from Japanese PatentApplication No. 2016-074328, filed on Apr. 1, 2016, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND Field of the Invention

The present invention relates to an acoustic matching member, anacoustic matching member group, and a medical imaging apparatus.

Related Art

An ultrasound imaging apparatus is known which captures an ultrasoundimage of a breast by scanning the breast with ultrasound waves in orderto use the ultrasound image for observation and diagnosis of the breasttissue of a subject. As such an ultrasound imaging apparatus, anultrasound imaging apparatus that captures an ultrasound image in astate in which a breast is compressed by a compression plate is known.In this ultrasound imaging apparatus, since the breast is compressed bythe compression plate, the subject feels uncomfortable.

Generally, in the case of capturing an ultrasound image, an acousticmatching member is provided between an ultrasound probe and a breast inorder to reduce acoustic impedance mismatch. Therefore, there is atechnique for reducing the burden on a subject using an acousticmatching member. For example, JP2005-270677A discloses a technique forreducing the discomfort of a subject by making the compression pressure,with which the breast is compressed, be distributed using an acousticmatching member.

However, since the technique disclosed in JP2005-270677A is for makingthe compression pressure, with which the breast is compressed, bedistributed using an acoustic matching member, there is room forimprovement in order to reduce the burden on the subject.

SUMMARY

The invention has been made in view of the above situation, and it is anobject of the invention to provide an acoustic matching member, anacoustic matching member group, and a medical imaging apparatus capableof reducing a burden on a subject in the case of imaging the breast ofthe subject with ultrasound waves in a state in which the breast iscompressed by a compression plate.

In order to achieve the aforementioned object, an acoustic matchingmember of the invention is an acoustic matching member located between abreast and a compression plate. A protruding portion that protrudestoward an imaging table disposed opposite to a compression plate isprovided in an end portion on a deepest side when viewed from a chestwall side of a subject in a case of compressing a breast of the subjectin contact with the compression plate.

A thickness of the acoustic matching member of the invention on thechest wall side of the subject may be smaller than that in the endportion on the deepest side.

A surface of the acoustic matching member of the invention that is incontact with the breast of the subject may have a recessed shape that isrecessed toward a central portion from an end portion in a horizontaldirection of the subject.

The acoustic matching member of the invention may have a protrudingshape that protrudes toward the imaging table.

The acoustic matching member of the invention may have a higher hardnessthan a hardness set in advance as a hardness of the breast.

In order to achieve the aforementioned object, an acoustic matchingmember group of the invention comprises: the acoustic matching member ofthe invention; and an upper acoustic matching member provided on asurface of the compression plate opposite to a surface facing theimaging table in a case of compressing the breast of the subject incontact with the compression plate.

A static friction coefficient of the acoustic matching member of theacoustic matching member group of the invention may be larger than astatic friction coefficient of the upper acoustic matching member.

A thickness of the acoustic matching member of the acoustic matchingmember group of the invention in a compression direction of thecompression plate may be larger than a thickness of the upper acousticmatching member.

The upper acoustic matching member of the acoustic matching member groupof the invention may be provided in a region of the compression plateother than a region corresponding to the protruding portion.

In order to achieve the aforementioned object, a medical imagingapparatus of the invention comprises: the acoustic matching member ofthe invention; an imaging table on which the breast of the subject isplaced; a compression plate that compresses the breast in contact withthe acoustic matching member; and an ultrasound imaging unit thatcaptures an ultrasound image of the breast.

The medical imaging apparatus of the invention may further comprise: acontact sensor that detects contact of the protruding portion of theacoustic matching member with the imaging table; and a control unit thatperforms control to reduce a compression pressure of the breast by thecompression plate in a case where the contact sensor detects contact ofthe protruding portion while the compression plate is compressing thebreast.

In order to achieve the aforementioned object, a medical imagingapparatus of the invention comprises: the acoustic matching member groupof the invention; an imaging table on which the breast of the subject isplaced; a compression plate that compresses the breast in contact withthe acoustic matching member group; and an ultrasound imaging unit thatcaptures an ultrasound image of the breast.

The medical imaging apparatus of the invention may further comprise aradiographic imaging unit that captures a radiographic image of thebreast.

In the invention, it is possible to provide a medical imaging apparatus,an imaging control method, and an imaging control program capable ofreducing the burden on the subject in the case of imaging the breast ofthe subject with ultrasound waves in a state in which the breast iscompressed by the compression plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing the appearance of an imaging unit of amedical imaging apparatus of a first embodiment.

FIG. 2 is a block diagram showing the configuration of the medicalimaging apparatus of the first embodiment.

FIG. 3 is a perspective view of an acoustic matching member of Example1-1 in the first embodiment.

FIG. 4 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 3interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast and a side view when the stateis viewed from the side surface of the subject.

FIG. 5 is a flowchart showing an imaging operation in a continuousimaging mode in which the medical imaging apparatus of the firstembodiment continuously captures a radiographic image and an ultrasoundimage.

FIG. 6 is a flowchart showing the breast compression processing flow ofthe medical imaging apparatus of the first embodiment.

FIG. 7 is a perspective view of an acoustic matching member of Example1-2 in the first embodiment.

FIG. 8 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 7interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast and a side view when the stateis viewed from the side surface of the subject.

FIG. 9 is a perspective view of an acoustic matching member of Example1-3 in the first embodiment.

FIG. 10 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 9interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast, a side view when the state isviewed from the side surface of the subject, and a cross-sectional viewtaken along the line A-A in the side view.

FIG. 11 is a perspective view of an acoustic matching member of Example1-4 in the first embodiment.

FIG. 12 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 11interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast, a side view when the state isviewed from the side surface of the subject, and a cross-sectional viewtaken along the line A-A in the side view.

FIG. 13 is a front view when a state, in which a compression platecompresses a breast with an acoustic matching member of Example 2-1 in asecond embodiment interposed between the compression plate and thebreast, is viewed from the direction of the nipple of the breast and aside view when the state is viewed from the side surface of the subject.

FIG. 14 is a flowchart showing an imaging operation in a continuousimaging mode in which a medical imaging apparatus of the secondembodiment continuously captures a radiographic image and an ultrasoundimage.

FIG. 15 is a front view when a state, in which a compression platecompresses a breast with an acoustic matching member of Example 2-2 inthe second embodiment interposed between the compression plate and thebreast, is viewed from the direction of the nipple of the breast and aside view when the state is viewed from the side surface of the subject.

FIG. 16 is a front view when a state, in which a compression platecompresses a breast with an acoustic matching member interposed betweenthe compression plate and the breast in a case where an upper acousticmatching member in the second embodiment has a protruding portionprotruding toward an imaging table, is viewed from the direction of thenipple of the breast and a side view when the state is viewed from theside surface of the subject.

FIG. 17 is a perspective view of an acoustic matching member of Example3-1 in a third embodiment.

FIG. 18 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 17interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast and a side view when the stateis viewed from the side surface of the subject.

FIG. 19 is a perspective view of an acoustic matching member of Example3-2 in the third embodiment.

FIG. 20 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 19interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast and a side view when the stateis viewed from the side surface of the subject.

FIG. 21 is a perspective view of an acoustic matching member of Example3-3 in the third embodiment.

FIG. 22 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 21interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast and a side view when the stateis viewed from the side surface of the subject.

FIG. 23 is a perspective view of an acoustic matching member of Example3-4 in the third embodiment.

FIG. 24 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 23interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast and a side view when the stateis viewed from the side surface of the subject.

FIG. 25 is a perspective view of an acoustic matching member of Example3-5 in the third embodiment.

FIG. 26 is a front view when a state, in which a compression platecompresses a breast with the acoustic matching member shown in FIG. 25interposed between the compression plate and the breast, is viewed fromthe direction of the nipple of the breast and a side view when the stateis viewed from the side surface of the subject.

DETAILED DESCRIPTION

Hereinafter, embodiments of the invention will be described in detailwith reference to the diagrams. In addition, these embodiments do notlimit the invention.

[First Embodiment]

EXAMPLE 1-1

First, the configuration of a medical imaging apparatus according to thepresent embodiment will be described with reference to FIG. 1.

A medical imaging apparatus 10 of the present embodiment has a functionof a radiation mammography apparatus, which captures a radiographicimage by emitting a radiation R to the breast of a subject and detectingthe radiation R transmitted through the breast, and a function of anultrasound imaging apparatus, which captures an ultrasound image bytransmitting an ultrasound wave to the breast of the subject andreceiving an ultrasound echo reflected from the inside of the breast.Hereinafter, the capturing of a radiographic image and the capturing ofan ultrasound image are simply referred to as “capturing” in a casewhere these are collectively described without distinction.

As shown in FIG. 1, the medical imaging apparatus 10 of the presentembodiment includes an arm unit 20, a base 22, and a shaft unit 24. Thebase 22 holds the arm unit 20 so as to be movable in a verticaldirection (Z-axis direction). The shaft unit 24 connects the arm unit 20to the base 22. The arm unit 20 can rotate relatively with respect tothe base 22 with the shaft unit 24 as a rotary axis.

A radiation emitting section 25, an imaging table 31, a compressionplate 32, a compression plate moving mechanism 34, an ultrasound probe36, and a probe moving mechanism 38 are provided in the arm unit 20.

The radiation emitting section 25 includes a radiation tube 26, a filter28, and a high voltage generating section 29. The radiation tube 26generates the radiation R when a tube voltage is applied. The filter 28is formed of a material, such as molybdenum (Mo) or rhodium (Rh), sothat a desired wavelength component among a plurality of wavelengthcomponents included in the radiation R generated by the radiation tube26 is selectively transmitted therethrough.

In the case of performing imaging, the breast of a subject is positionedon an imaging surface 35 of the imaging table 31. The imaging table 31or the like with which the breast of the subject is in contact is formedof, for example, carbon from the viewpoint of the transparency orintensity of the radiation R. A radiation detector 30 for detecting theradiation R transmitted through the breast and the imaging table 31 isdisposed inside the imaging table 31. A radiographic image is generatedbased on the radiation R detected by the radiation detector 30. The typeof the radiation detector 30 of the present embodiment is notparticularly limited, and may be an indirect conversion type radiationdetector that converts the radiation R into light and converts theconverted light into electric charges or may be a direct conversion typeradiation detector that converts the radiation R directly into electriccharges, for example.

A contact sensor 39 for detecting the contact of an object with respectto the imaging table 31 is disposed inside the imaging table 31.Specifically, the contact sensor 39 of the present embodiment detectswhether or not a protruding portion 50A (refer to FIGS. 3 and 4) of anacoustic matching member 50 has come into contact with the imaging table31. As a specific example of the contact sensor 39, a pressure sensorfor detecting the pressure that is applied to the imaging table 31 bythe contact of the acoustic matching member 50 can be mentioned, but thecontact sensor 39 is not limited thereto.

The compression plate 32 is moved in the vertical direction (Z-axisdirection) by the compression plate moving mechanism 34, so that thebreast of the subject is compressed between the compression plate 32 andthe imaging table 31. It is preferable that the compression plate 32 isoptically transparent in order to check positioning or the compressionstate in compression of the breast, and is formed of a materialexcellent in transparency with respect to the radiation R so that theradiation R emitted from the radiation emitting section 25 is easilytransmitted therethrough. In addition, it is preferable that thecompression plate 32 is formed of a material through which ultrasoundwaves transmitted from the ultrasound probe 36 easily propagate. As amaterial of the compression plate 32, for example, a resin such aspolymethylpentene, polycarbonate, acrylic, and polyethyleneterephthalate can be used. In particular, polymethylpentene has lowstiffness and excellent stretchability and flexibility and has suitablephysical property values in terms of acoustic impedance affecting thereflectance of ultrasound waves and an attenuation coefficient affectingthe attenuation of ultrasound waves. Therefore, polymethylpentene has issuitable as a material of the compression plate 32.

The ultrasound probe 36 is moved along the upper surface (surfaceopposite to a surface in contact with the breast of the subject) of thecompression plate 32 by the probe moving mechanism 38, and scans thebreast with ultrasound waves to acquire an ultrasound image of thebreast. The ultrasound probe 36 includes a plurality of ultrasoundtransducers (not shown) arranged in a one-dimensional manner or in atwo-dimensional manner. Each of the ultrasound transducers transmitsultrasound waves based on the applied driving signal and receives theultrasound echo to output the reception signal.

Each of the plurality of ultrasound transducers is configured by atransducer in which electrodes are formed at both ends of apiezoelectric material (piezoelectric body), such as piezoelectricceramic represented by lead (Pb) zirconate titanate (PZT) and a polymerpiezoelectric element represented by polyvinylidene difluoride (PVDF),for example. When a pulsed or continuous-wave driving signal istransmitted to the electrodes of the transducer to apply a voltage, thepiezoelectric body expands and contracts. Due to the expansion andcontraction, pulsed or continuous-wave ultrasound waves are generatedfrom each transducer, and these ultrasound waves are combined to form anultrasound beam. Each transducer expands and contracts by receivingpropagating ultrasound waves, thereby generating an electric signal. Theelectric signal is output from the transducer as a reception signal ofultrasound waves, and is input to a control unit 40 (refer to FIG. 2)through a cable (not shown).

In the medical imaging apparatus 10 of the present embodiment, in thecase of performing ultrasound imaging, the control unit 40 (refer toFIG. 2) moves the ultrasound probe 36 using the probe moving mechanism38 so that an ultrasound image is automatically captured without theoperator moving the ultrasound probe 36. Without being limited to thepresent embodiment, the operator may move the ultrasound probe 36 tocapture an ultrasound image.

As shown in FIG. 2, the medical imaging apparatus 10 of the presentembodiment includes a pressure sensor 33, a position sensor 37, thecontrol unit 40, a storage unit 42, an operation panel 44, and aninterface (I/F) unit 46. The radiation emitting section 25, theradiation detector 30, the pressure sensor 33, the compression platemoving mechanism 34, the ultrasound probe 36, the position sensor 37,the probe moving mechanism 38, the control unit 40, the storage unit 42,the operation panel 44, and the interface (I/F) unit 46 are connected toeach other so that transmission and reception of various signalstherebetween are possible through a bus 49, such as a system bus or acontrol bus.

The control unit 40 includes a central processing unit (CPU) 40A, a readonly memory (ROM) 40B, and a random access memory (RAM) 40C. Variousprograms executed by the CPU 40A are stored in advance in the ROM 40B.The RAM 40C stores various kinds of data temporarily.

The pressure sensor 33 detects the compression pressure by thecompression plate 32. The position sensor 37 is built into theultrasound probe 36, and detects the position (position on the surfaceof compression plate 32) of the ultrasound probe 36.

The control unit 40 controls the overall operation of the medicalimaging apparatus 10. In the case of capturing a radiographic image, thecontrol unit 40 of the present embodiment controls the radiationemitting section 25, the radiation detector 30, and the compressionplate moving mechanism 34. Based on the detection result of the pressuresensor 33, the control unit 40 moves the compression plate 32 using thecompression plate moving mechanism 34 so that the breast is compressedbetween the compression plate 32 and the imaging table 31. The controlunit 40 applies a high voltage generated by the high voltage generatingsection 29 to the radiation tube 26 by adjusting the imaging conditions,such as a tube voltage or a tube current, so that the radiation R isemitted from the radiation emitting section 25. The control unit 40causes the radiation detector 30 to detect the radiation R transmittedthrough the breast, thereby capturing a radiographic image.

In the case of capturing an ultrasound image, the control unit 40 of thepresent embodiment controls the ultrasound probe 36 and the probe movingmechanism 38. The control unit 40 checks the position of the ultrasoundprobe 36 based on the detection result of the position sensor 37, andmoves the ultrasound probe 36 using the probe moving mechanism 38. Thecontrol unit 40 captures an ultrasound image by transmitting andreceiving ultrasound waves while moving the ultrasound probe 36 usingthe probe moving mechanism 38.

Image data, other various kinds of information, and the like ofradiographic images and ultrasound images obtained by imaging are storedin the storage unit 42. As specific examples of the storage unit 42, ahard disk drive (HDD), a solid state drive (SSD), and the like can bementioned.

The operation panel 44 receives an instruction (for example, aninstruction to compress the breast with the compression plate 32)regarding imaging by the operator. The operation panel 44 is provided inthe arm unit 20 of the medical imaging apparatus 10, for example. Inaddition, the operation panel 44 may be provided as a touch panel inwhich a display unit and an input unit are combined.

The I/F unit 46 communicates various kinds of information with anexternal device (not shown), such as a console, or an external system(for example, a radiology information system (RIS; not shown)), bywireless communications or cable communication. in the medical imagingapparatus 10 of the present embodiment, the captured radiographic imageor ultrasound image is transmitted from the I/F unit 46 to an externaldevice, such as a console, or an external device, such as an imageinterpretation device.

Next, capturing of a radiographic image and an ultrasound image in themedical imaging apparatus 10 of the present embodiment will bedescribed.

The medical imaging apparatus 10 of the present embodiment has animaging mode for continuously capturing a radiographic image and anultrasound image (hereinafter, referred to as a “continuous imagingmode”) and an imaging mode for capturing one of a radiographic image andan ultrasound image. Hereinafter, a case where the medical imagingapparatus 10 executes the continuous imaging mode will be described.

In the medical imaging apparatus 10 of the present embodiment, in thecase of capturing an ultrasound image of a breast in a state in whichthe breast is compressed by the compression plate 32, the acousticmatching member 50 whose example is shown in FIGS. 3 and 4 is providedbetween the compression plate 32 and the breast in order to reduce theacoustic impedance mismatch at the contact surface between thecompression plate 32 and the breast. FIG. 3 shows a perspective view ofthe acoustic matching member 50, and FIG. 4 shows a front view when astate, in which the compression plate 32 compresses the breast N withthe acoustic matching member 50 interposed between the compression plate32 and the breast N, is viewed from the direction of the nipple of thebreast N and a side view when the state is viewed from the side surfaceof the subject.

As shown in FIGS. 3 and 4, in the acoustic matching member 50 of thepresent embodiment, the protruding portion 50A that protrudes toward theimaging table 31 is provided in an end portion on the nipple side of thesubject (end portion on the deepest side when viewed from the chest wallof the subject). As shown in FIG. 4, in the space formed by the acousticmatching member 50 and the imaging table 31, the breast N is compressedby the compression plate 32. In the acoustic matching member 50 of thepresent embodiment, the protruding portion 50A is not in contact withthe imaging table 31 in a state in which the breast N is compressed.Therefore, the length of the protruding portion 50A that protrudestoward the imaging table 31 is determined based on the thickness(thickness in the Z-axis direction) when the general breast N iscompressed in capturing of a radiographic image and an ultrasound image.

On the other hand, the thickness of a portion of the acoustic matchingmember 50 in contact with the breast N is the same on the entirerectangular surface in contact with the compression plate 32, and thespecific thickness may be determined, for example, from the viewpoint ofmatching the acoustic impedance. The length of each side of the acousticmatching member 50 on the rectangular surface in contact with thecompression plate 32 is the same as the length of each side of thecompression plate 32 on a surface in contact with the acoustic matchingmember 50. By the setting of such a length, in a case where the operatorperforms positioning of the acoustic matching member 50, it issufficient to match the shape of the compression plate 32. Accordingly,the positioning becomes easy. In the present embodiment, “same” refersto a range that can be regarded as the same, including an error or anallowable range.

In the present embodiment, the acoustic matching member 50 is formed ofa material having both good compatibility with a living body (breast Nin the present embodiment) and good transparency of ultrasound waves. Itis preferable that the acoustic matching member 50 is formed of amaterial that is flexible, has physical strength and good transparencyof ultrasound waves, and can withstand sterilization treatment. Asmaterials of the acoustic matching member 50, a non-hydrogel material, apolymeric hydrogel, and the like are used. As specific materials of theacoustic matching member 50, carboxyvinyl polymer, glycerin, polyvinylpyrrolidone (PVP), polyurethane, polyvinyl alcohol (PVA) based polymergel, urethane rubber, silicone rubber, polyethylene oxide (PEO), and thelike are used. The surface of the acoustic matching member 50 of thepresent embodiment may be covered with silicone rubber or the like inorder to maintain the shape.

In the present embodiment, it is preferable that the hardness of theacoustic matching member 50 is higher than the hardness of the generalbreast N (in other words, the acoustic matching member 50 is harder thanthe general breast N). In addition, it is preferable that the hardnessof the acoustic matching member 50 is lower than the hardness of thecompression plate 32 (in other words, the acoustic matching member 50 issofter than the compression plate 32). By setting the hardness of theacoustic matching member 50 as described above, the effect of uniformlycompressing the breast N in a desired shape is enhanced, and the effectof suppressing excessive compression of the breast N is enhanced.

For the hardness of the acoustic matching member 50, it is preferablethat, in the Y-axis direction, the hardness on the chest wall side ofthe breast N is lower than the hardness on the nipple side (in otherwords, the acoustic matching member 50 on the chest wall side of thebreast N is softer than the acoustic matching member 50 on the nippleside). In this case, since the acoustic matching member 50 tends to bedeformed on the chest wall side compared with the nipple side, theacoustic matching member 50 is likely to be deformed according to theshape of the breast N. Therefore, it is possible to reduce the burden onthe subject.

A method of placing the acoustic matching member 50 on the upper surfaceof the breast N is not particularly limited. In a case where theacoustic matching member 50 is attachable to the surface of thecompression plate 32 on the breast side, the breast N may be compressedby the compression plate 32 in a state in which the acoustic matchingmember 50 is attached to the compression plate 32. In addition, thebreast N may also be compressed by the compression plate 32 in a statein which the operator has placed the acoustic matching member 50 on thebreast N.

In the case of executing the continuous imaging mode in the medicalimaging apparatus 10 of the present embodiment, both the capturing of aradiographic image and the capturing of an ultrasound image arecontinuously performed in a state in which the compression plate 32compresses the breast until the end of the capturing of a radiographicimage and the capturing of an ultrasound image, without releasing thecompression of the breast. Therefore, as shown in FIG. 4, capturing of aradiographic image and capturing of an ultrasound image are performed ina state in which the acoustic matching member 50 required in thecapturing of an ultrasound image is provided between the compressionplate 32 and the breast N.

FIG. 5 shows the overall flow of a series of imaging operations in acase where the operator captures a radiographic image and an ultrasoundimage in the continuous imaging mode using the medical imaging apparatus10 of the present embodiment.

First, the control unit 40 of the medical imaging apparatus 10 acquiresan imaging menu in step S100. The imaging menu includes information,such as imaging conditions, a subject, and the breast N. For example,the control unit 40 may acquire an imaging menu from an external device,such as a console, through the I/F unit 46, or may acquire an imagingmenu that the operator inputs through the operation panel 44.

In the next step S102, the operator positions the breast N of thesubject on the imaging table 31.

Then, in the next step S104, the medical imaging apparatus 10 performsbreast compression processing (refer to FIG. 6) for compressing thebreast N of the subject with the compression plate 32 in a state inwhich the acoustic matching member 50 is provided on the upper surface(surface on the compression plate 32 side) of the breast N, which willbe described in detail later.

In the next step S106, the medical imaging apparatus 10 captures aradiographic image of the breast N. In the case of capturing aradiographic image, the control unit 40 retracts the ultrasound probe 36to the outside of the radiographic image detection region of theradiation detector 30 using the probe moving mechanism 38. The imagedata of the captured radiographic image may be output to an externaldevice, such as a console, immediately after capturing the radiographicimage. Alternatively, the image data of the captured radiographic imagemay be temporarily stored in the storage unit 42, and image data of bothimages may be output to an external device, such as a console, after theend of the capturing of a radiographic image and an ultrasound image.

After the end of the capturing of the radiographic image, the medicalimaging apparatus 10 captures an ultrasound image of the breast N in thenext step S108. As described above, the control unit 40 causes the probemoving mechanism 38 to move the ultrasound probe 36 along the surface ofthe compression plate 32 facing the radiation tube 26 while causing theposition sensor 37 to detect the position of the ultrasound probe 36.Then, the control unit 40 captures an ultrasound image by transmittingan ultrasound wave to the breast N from the ultrasound probe 36 andreceiving the ultrasound echo reflected from the inside of the breast N.

After the end of the capturing of the ultrasound image, the medicalimaging apparatus 10 releases the compression of the breast N by thecompression plate 32 in the next step S110. Specifically, the operatorinputs an instruction to move the compression plate 32 (instruction torelease the compression) through the operation panel 44. The controlunit 40 releases the compression of the breast N by moving thecompression plate 32 in a direction away from the imaging table 31 usingthe compression plate moving mechanism 34 in accordance with theinstruction input of the operator.

When the compression of the breast N is released in this manner, theimaging operation in the continuous imaging mode ends.

Next, the breast compression processing of the present embodimentexecuted in above step S104 will be described with reference to FIG. 6.FIG. 6 is a flowchart of an example of the breast compression processingexecuted by the control unit 40 in step S104.

In the medical imaging apparatus 10 of the present embodiment, when thepositioning of the breast N of the subject is completed, the operatorinputs a compression instruction to move the compression plate 32through the operation panel 44. When the compression instruction isreceived, the control unit 40 executes the breast compression processingshown in FIG. 6.

In step S200, the control unit 40 starts the movement of the compressionplate 32. Specifically, the control unit 40 causes the compression platemoving mechanism 34 to move the compression plate 32 in a directionmoving closer to the imaging table 31.

In the next step S202, the control unit 40 determines whether or not theacoustic matching member 50 has come into contact with the imaging table31 based on the detection result of the contact sensor 39. In a casewhere the acoustic matching member 50 is not in contact with the imagingtable 31, negative determination is made, and the process proceeds tostep S204.

In step S204, the control unit 40 determines whether or not to stop thecompression plate 32. In the medical imaging apparatus 10 of the presentembodiment, in the case of performing imaging, a desired compressionpressure for compressing the breast N is determined in advance in theapparatus. Therefore, in this step, the control unit 40 determineswhether or not to stop the compression plate 32 according to whether ornot the compression pressure detected by the pressure sensor 33 hasreached a desired compression pressure. In a case where the compressionpressure detected by the pressure sensor 33 has not reached a desiredcompression pressure, negative determination is made, and the processreturns to step S202. On the other hand, in a case where the compressionpressure detected by the pressure sensor 33 has reached a desiredcompression pressure, positive determination is made, and the processproceeds to step S220.

On the other hand, in a case where the acoustic matching member 50 hascome into contact with the imaging table 31 in step S202, positivedetermination is made, and the process proceeds to step S206.

In step S206, the control unit 40 stops the movement of the compressionplate 32. Then, in the next step S208, the control unit 40 starts themovement of the compression plate 32 in the opposite direction.Specifically, the control unit 40 causes the compression plate movingmechanism 34 to move the compression plate 32 in a direction away fromthe imaging table 31. In this step, the distance by which the controlunit 40 moves the compression plate 32 is not particularly limited, andthe compression plate 32 may be moved to a position where compressionagainst the breast N is completely released, or the compression plate 32may be moved by a predetermined distance regardless of whether or notcompression is completely released.

In the next step S210, the control unit 40 determines whether or not tocontinue compressing the breast N. In the present embodiment, asdescribed above, in a case where the acoustic matching member 50 hascome into contact with the imaging table 31, there is a concern that thebreast N is excessively compressed regardless of the compressionpressure. Accordingly, the control unit 40 stops the movement of thecompression plate 32 in step S206 and moves the compression plate 32 ina direction away from the imaging table 31 in step S208, therebyreducing the burden (compression) on the subject. However, depending onthe shape, state, or the like of the breast N of the subject, even in acase where the acoustic matching member 50 has come into contact withthe imaging table 31, the burden on the subject that is applied bycompressing the compression plate 32 may not be large, and it may benecessary to further compress the breast N. In such a case, in themedical imaging apparatus 10 of the present embodiment, it is possibleto continue compressing the breast N even after the acoustic matchingmember 50 has come into contact with the imaging table 31. In such acase, therefore, the operator inputs an instruction to continuecompressing the compression plate 32 through the operation panel 44.

In a case where no compression continuation instruction is received evenafter the passage of a predetermined amount of time, negativedetermination is made in step S210, and the process proceeds to stepS212. In step S212, the control unit 40 determines whether or not tocontinue imaging. Before the compression pressure for compressing thebreast N reaches a desired compression pressure, the acoustic matchingmember 50 comes into contact with the imaging table 31. Accordingly, ina case where compression is not continued, even if the breast N iscompressed again by the compression plate 32, there is a highpossibility that the acoustic matching member 50 will come into contactwith the imaging table 31 before the compression pressure forcompressing the breast N reaches the desired compression pressure.However, even in a state in which the compression pressure forcompressing the breast N does not reach the desired compressionpressure, the operator may desire to continue imaging. In such a case,the operator inputs an instruction to continue the imaging through theoperation panel 44.

In a case where no imaging continuation instruction is received evenafter the passage of a predetermined amount of time, negativedetermination is made in step S212, and this breast compressionprocessing is ended. At the same time, the imaging operation itselfshown in FIG. 5 is ended.

On the other hand, in a case where an imaging continuation instructionis received, positive determination is made in step S212, and theprocess proceeds to step S214. In step S214, the control unit 40 movesthe compression plate 32 to a predetermined position in a directionmoving closer to the imaging table 31, and ends this breast compressionprocessing. The predetermined position is not particularly limited. Forexample, a position where the distance between the acoustic matchingmember 50 and the imaging table 31 takes a value considering the size ofthe general breast N or the like may be set in the apparatus in advanceas the predetermined position. Without being limited to this, thecontrol unit 40 may stop the movement of the compression plate 32 inresponse to a stop instruction to stop the movement of the compressionplate 32 that has been input through the operation panel 44 by theoperator.

On the other hand, in a case where a compression continuationinstruction is received in the above step S210, positive determinationis made, and the process proceeds to step S216. In step S216, thecontrol unit 40 starts the movement of the compression plate 32 in adirection moving closer to the imaging table 31.

In the next step S218, the control unit 40 determines whether or not tostop the compression plate 32. In this step, the control unit 40 stopsthe movement of the compression plate 32 in at least one of a case wherethe compression pressure detected by the pressure sensor 33 reaches adesired compression pressure or a case where a stop instruction isreceived. In a case where the movement of the compression plate 32 isnot to be stopped, negative determination is made to enter a standbystate. On the other hand, in a case where the movement of thecompression plate 32 is to be stopped, positive determination is made,and the process proceeds to step S220.

In step S220, the control unit 40 stops the movement of the compressionplate 32, and then ends this breast compression processing.

The shape of the acoustic matching member 50 in the present embodimentis not limited to the shape shown in FIGS. 3 and 4, and may be a shapein which the protruding portion 50A that protrudes toward the imagingtable 31 is provided in an end portion on the nipple side of the subject(end portion on the deepest side when viewed from the chest wall of thesubject). The shape of the acoustic matching member shown in FIGS. 3 and4 is assumed to be Example 1-1, and other shapes of the acousticmatching member of the present embodiment will be described in thefollowing examples.

EXAMPLE 1-2

FIG. 7 shows a perspective view of an acoustic matching member 52 ofthis example, and FIG. 8 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 52 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N and a sideview when the state is viewed from the side surface of the subject.

As shown in FIGS. 7 and 8, the acoustic matching member 52 of thisexample has a protruding portion 52A in the same manner as the acousticmatching member 50 (refer to FIGS. 3 and 4) of the example describedabove, but the thickness of a portion in contact with the breast Nchanges along the Y-axis direction.

As shown in FIGS. 7 and 8, in the acoustic matching member 52 of thisexample, the thickness of a portion in contact with the breast N is thesmallest on the chest wall side and the largest on the nipple side.

In general, the thickness of the breast N in the vertical direction ofthe subject increases toward the chest wall side and decreases towardthe nipple side. Therefore, by forming the acoustic matching member 52in the shape shown in FIGS. 7 and 8, it is possible to performcompression according to the shape of the breast N. As a result, it ispossible to reduce the compression pressure applied to the chest wallside. Thus, according to the acoustic matching member 52 of thisexample, it is possible to reduce the burden on the subject at the timeof compression using the compression plate 32.

EXAMPLE 1-3

FIG. 9 shows a perspective view of an acoustic matching member 54 ofthis example, and FIG. 10 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 54 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N, a side viewwhen the state is viewed from the side surface of the subject, and across-sectional view taken along the line A-A in the side view.

As shown in FIGS. 9 and 10, the acoustic matching member 54 of thisexample has a protruding portion 54A in the same manner as the acousticmatching member 50 (refer to FIGS. 3 and 4) of the example describedabove, but the thickness of a portion in contact with the breast Nchanges along the X-axis direction.

As shown in FIGS. 9 and 10, in the acoustic matching member 54 of thisexample, the shape of a portion in contact with the breast N is arecessed shape that is recessed toward the central portion from the endportion in the horizontal direction of the subject.

In general, the thickness of the breast N in the horizontal direction(corresponding to the X-axis direction in the diagram) of the subjectincreases toward the central portion and decreases toward the endportion. Therefore, by forming the acoustic matching member 54 in theshape shown in FIGS. 9 and 10, it is possible to perform compressionaccording to the shape of the breast N. As a result, it is possible toreduce the compression pressure applied to the chest wall side. Thus,according to the acoustic matching member 54 of this example, it ispossible to reduce the burden on the subject at the time of compressionusing the compression plate 32.

EXAMPLE 1-4

FIG. 11 shows a perspective view of an acoustic matching member 56 ofthis example, and FIG. 12 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 56 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N, a side viewwhen the state is viewed from the side surface of the subject, and across-sectional view taken along the line A-A in the side view.

As shown in FIGS. 11 and 12, the acoustic matching member 56 of thisexample has a protruding portion 56A in the same manner as the acousticmatching member 50 (refer to FIGS. 3 and 4) of the example describedabove, but the thickness of a portion in contact with the breast Nchanges along the X-axis direction.

As shown in FIGS. 11 and 12, in the acoustic matching member 56 of thisexample, the shape of a portion in contact with the breast N is aprotruding shape that protrudes toward the imaging table 31.Specifically, the thickness of a portion of the acoustic matching member56 in contact with the breast N is the largest in a central portion ofthe compression plate 32 in the X-axis direction, and is the smallest inan end portion of the compression plate 32 in the X-axis direction.

In general, the thickness of the breast N in the horizontal direction ofthe subject increases toward the central portion and decreases towardthe end portion. Therefore, in order to make the thickness of the breastN uniform in the case of compressing the breast N with the compressionplate 32, it is preferable to compress the central portion more than theend portion in the horizontal direction of the subject. By forming theacoustic matching member 54 in the shape shown in FIGS. 11 and 12, it ispossible to increase the compression pressure toward the central portionin the horizontal direction of the breast N. As a result, it becomeseasy to make the thickness of the breast N uniform.

[Second Embodiment]

EXAMPLE 2-1

Next, a second embodiment will be described. The same portions as in themedical imaging apparatus 10 and the acoustic matching member of thefirst embodiment are denoted by the same reference numerals, and thedetailed explanation thereof will be omitted.

Since the configuration of the medical imaging apparatus 10 is the sameas that of the medical imaging apparatus 10 (refer to FIGS. 1 and 2) ofthe first embodiment, the explanation thereof will be omitted.

In the medical imaging apparatus 10 of the first embodiment describedabove, in the case of capturing an ultrasound image, one of the acousticmatching members 50 to 56 is provided between the compression plate 32and the breast N. In contrast, the medical imaging apparatus 10 of thepresent embodiment, in the case of capturing an ultrasound image, one ofthe acoustic matching members 50 to 56 is provided between thecompression plate 32 and the breast N, and an upper acoustic matchingmember is provided on the upper surface (surface not facing the imagingtable 31) of the compression plate 32. Hereinafter, a case where theacoustic matching member 50 described in the above Example 1-1 isprovided between the compression plate 32 and the breast N will bedescribed as a specific example.

FIG. 13 shows a front view when a state, in which the compression plate32 compresses the breast N with the acoustic matching member 50interposed between the compression plate 32 and the breast N, is viewedfrom the direction of the nipple of the breast N and a side view whenthe state is viewed from the side surface of the subject.

As shown in FIG. 13, in the present embodiment, the acoustic matchingmember 50 is provided between the compression plate 32 and the breast N,and an upper acoustic matching member 60 is provided on the uppersurface of the compression plate 32. In the case of capturing anultrasound image, the control unit 40 causes the probe moving mechanism38 to move the ultrasound probe 36 along the upper surface of thecompression plate 32 in a state in which the upper acoustic matchingmember 60 is provided.

The upper acoustic matching member 60 of the present embodiment has afunction as a lubricant in the movement of the ultrasound probe 36 and afunction of reducing an acoustic impedance mismatch on the contactsurface between the compression plate 32 and the ultrasound probe 36.

The upper acoustic matching member 60 of the present embodiment is arectangular parallelepiped having the same area as the contact surfaceof the compression plate 32. As shown in FIG. 13, the thickness of theupper acoustic matching member 60 in the Z-axis direction is smallerthan the thickness of the acoustic matching member 50 in the Z-axisdirection. As a specific example of the thickness of the acousticmatching member 50 in the Z-axis direction, 1 mm or more can bementioned.

The acoustic matching member 50 preferably has high adhesion to thebreast N, and the upper acoustic matching member 60 preferably has highlubricity in order to move the ultrasound probe 36 smoothly. In thepresent embodiment, therefore, the static friction coefficient of theacoustic matching member 50 is larger than the static frictioncoefficient of the upper acoustic matching member 60. As a specificexample of the static friction coefficient, 0.2 or more can be mentionedfor the acoustic matching member 50, and 0.2 or less can be mentionedfor the upper acoustic matching member 60.

In the present embodiment, the upper acoustic matching member 60 isformed of a material having both good lubricity and transparency ofultrasound waves. As the upper acoustic matching member 60 of thepresent embodiment, a so-called gel pad in which the surface is coveredwith silicone rubber or the like in order to maintain the shape is used.

As shown in FIG. 14, the overall flow of a series of imaging operationsin the case of performing imaging in the continuous imaging mode in themedical imaging apparatus 10 of the present embodiment is different fromthe overall flow (refer to FIG. 5) of the imaging operation of the firstembodiment in that processing in step S107 is performed between stepsS106 and S108.

As described above, in the medical imaging apparatus 10 of the presentembodiment, in the case of capturing an ultrasound image, the upperacoustic matching member 60 is provided on the upper surface of thecompression plate 32. Therefore, as shown in FIG. 14, after thecapturing of a radiographic image is ended, the operator places theupper acoustic matching member 60 on the upper surface of thecompression plate 32 in step S107.

Although the method of providing the upper acoustic matching member 60on the upper surface of the compression plate 32 is not particularlylimited, it is preferable that the upper acoustic matching member 60does not move and is in close contact with the compression plate 32 evenif the ultrasound probe 36 is moved on the upper surface of thecompression plate 32. For example, in a case where the compression plate32 has a mounting mechanism for mounting the upper acoustic matchingmember 60 to the upper surface, the upper acoustic matching member 60may be mounted on the upper surface of the compression plate 32 usingthe mounting mechanism.

In addition, since breast compression processing executed in the medicalimaging apparatus 10 of the present embodiment is the same as the breastcompression processing (refer to FIG. 6) executed in the medical imagingapparatus 10 of the first embodiment, the explanation thereof will beomitted.

The shape of the upper acoustic matching member 60 provided on the uppersurface of the compression plate 32 in the present embodiment is notlimited to the shape shown in FIG. 13, and any shape that covers theregion of the compression plate 32 to move the ultrasound probe 36 inthe capturing of an ultrasound image may be used. The shape of the upperacoustic matching member shown in FIG. 13 is assumed to be Example 2-1,and other shapes of the upper acoustic matching member of the presentembodiment will be described in the following examples.

EXAMPLE 2-2

FIG. 15 shows a front view when a state, in which the compression plate32 compresses the breast N with the acoustic matching member 50interposed between the compression plate 32 and the breast N, is viewedfrom the direction of the nipple of the breast N and a side view whenthe state is viewed from the side surface of the subject.

As shown in FIG. 15, an upper acoustic matching member 62 of thisexample is different from the upper acoustic matching member 60 (referto FIG. 13) of the example described above in terms of the area (size)of a portion in contact with the compression plate 32.

As shown in FIG. 15, the upper acoustic matching member 62 of thisexample is not present in a region of the upper surface of thecompression plate 32 corresponding to the protruding portion 52A of theacoustic matching member 50.

The breast N is not disposed in the region corresponding to theprotruding portion 50A of the acoustic matching member 50. Therefore, inthe case of capturing an ultrasound image, scanning by the ultrasoundprobe 36 is not required for the region of the upper surface of thecompression plate 32 corresponding to the protruding portion 52A of theacoustic matching member 50.

Thus, since the upper acoustic matching member 62 is not provided in theregion of the upper surface of the compression plate 32 corresponding tothe protruding portion 52A of the acoustic matching member 50, theoperator can easily recognize the imaging region of an ultrasound image(or the outside of the imaging region of an ultrasound image) based on aregion where the upper acoustic matching member 62 is provided.

Thus, the acoustic matching members 50 to 56 used in the medical imagingapparatus 10 of the first and second embodiments are acoustic matchingmembers located between the breast N and the compression plate 32. Inaddition, in the case of compressing the breast of the subject incontact with the compression plate 32, the protruding portions 50A to56A that protrude toward the imaging table 31 disposed opposite to thecompression plate 32 are provided in an end portion on the deepest side(nipple side) when viewed from the chest wall side of the subject.

In a space formed by the protruding portions 50A to 56A of the acousticmatching members 50 to 56 and the imaging table 31, the breast N iscompressed by the compression plate 32. In the compression of the breastN, since the protruding portions 50A to 56A are in contact with theimaging table 31, excessive compression of the breast N can besuppressed. Therefore, since unnecessary deformation of the breast canbe suppressed, it is possible to reduce the burden on the subject.

In the above first and second embodiments, the cases have been describedin which the acoustic matching members 50 to 56 having the protrudingportions 50A to 56A that protrude toward the imaging table 31 aredisposed between the compression plate 32 and the breast N. In thesecond embodiment described above, however, the shape of the upperacoustic matching member disposed on the upper surface of thecompression plate 32 may be a shape having a protruding portion thatprotrudes toward the imaging table 31. For example, as in an exampleshown in FIG. 16, an acoustic matching member 58 may be provided betweenthe compression plate 32 and the breast N, and an upper acousticmatching member 64 may be provided on the upper surface of thecompression plate 32.

As shown in FIG. 16, the acoustic matching member 58 is a rectangularparallelepiped in which a surface in contact with the compression plate32 has the same shape and area as the bottom surface of the compressionplate 32. On the other hand, the upper acoustic matching member 64covers the upper surface of the compression plate 32, the side surfaceof the compression plate 32 on the nipple side, and the side surface ofthe acoustic matching member 58 on the nipple side, and has a protrudingportion 64A that protrudes toward the imaging table 31 beyond the bottomsurface of the acoustic matching member 58.

Thus, in a case where the upper acoustic matching member 64 has theprotruding portion 64A that protrudes toward the imaging table 31 beyondthe bottom surface of the acoustic matching member 58, the breast N iscompressed by the compression plate 32 in a space formed by the acousticmatching member 58, the protruding portion 64A of the upper acousticmatching member 64, and the imaging table 31. Also in the presentembodiment, the upper acoustic matching member 64 has the protrudingportion 64A. Therefore, in the same manner as in the embodimentdescribed above, since excessive compression of the breast N can besuppressed, it is possible to reduce the burden on the subject.

[Third Embodiment]

Next, a third embodiment will be described. The same portions as in themedical imaging apparatus 10 and the acoustic matching member of eachembodiment described above are denoted by the same reference numerals,and the detailed explanation thereof will be omitted. Since theconfiguration of the medical imaging apparatus 10 is the same as that ofthe medical imaging apparatus 10 (refer to FIGS. 1 and 2) of the firstembodiment, the explanation thereof will be omitted.

In the medical imaging apparatus 10 of the present embodiment, similarto the medical imaging apparatus 10 of the second embodiment describedabove, in the case of capturing an ultrasound image, an acousticmatching member is provided between the compression plate 32 and thebreast N, and an upper acoustic matching member is provided on the uppersurface of the compression plate 32.

Therefore, the overall flow of a series of imaging operations in thecase of performing imaging in the continuous imaging mode in the medicalimaging apparatus 10 of the present embodiment is the same as theoverall flow (refer to FIG. 14) of the imaging operation of the secondembodiment. In addition, breast compression processing in the medicalimaging apparatus 10 of the present embodiment is the same as the breastcompression processing (refer to FIG. 6) of the first embodiment.

In the medical imaging apparatus 10 of the present embodiment, the typeof an acoustic matching member provided between the compression plate 32and the breast N may be different from the type of an upper acousticmatching member provided on the upper surface of the compression plate32, and the shapes of the acoustic matching member and the upperacoustic matching member are not limited to the shapes exemplified inthe first and second embodiments described above. Hereinafter, theshapes of the acoustic matching member and the upper acoustic matchingmember in the present embodiment will be described by way of examples.

EXAMPLE 3-1

FIG. 17 shows a perspective view of an acoustic matching member 70 ofthis example, and FIG. 18 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 70 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N and a sideview when the state is viewed from the side surface of the subject.

As shown in FIGS. 17 and 18, in the acoustic matching member 70 of thisexample, the thickness of a portion in contact with the breast N changesalong the X-axis direction. Specifically, as shown in FIGS. 17 and 18,in the acoustic matching member 70 of this example, the shape of aportion in contact with the breast N is a recessed shape that isrecessed toward the central portion from the end portion in thehorizontal direction of the subject.

The acoustic matching member 70 of this example is the same as theacoustic matching member 54 (refer to FIG. 10) of Example 1-3 of thefirst embodiment in that the shape of a portion in contact with thebreast is a recessed shape that is recessed toward the central portionfrom the end portion in the horizontal direction of the subject, but isdifferent from the acoustic matching member 54 (refer to FIG. 10) ofExample 1-3 of the first embodiment in that a protruding portioncorresponding to the protruding portion 54A provided in the acousticmatching member 54 is provided.

Therefore, as shown in FIGS. 17 and 18, the shape of the acousticmatching member 70 of this example when viewed from the direction of thenipple of the breast N is a recessed shape that is recessed toward thecentral portion from the end portion in the horizontal direction of thesubject.

In addition, as shown in FIG. 18, an upper acoustic matching member 80of this example is a rectangular parallelepiped in which a surface incontact with the compression plate 32 has the same area as the bottomsurface of the compression plate 32.

As described above in Example 1-3 of the first embodiment, in general,the thickness of the breast N in the horizontal direction of the subjectincreases toward the nipple portion and decreases toward the left andright end portions of the subject. Therefore, by forming the acousticmatching member 70 in the shape shown in FIGS. 17 and 18, it is possibleto perform compression according to the shape of the breast N. As aresult, it is possible to reduce the compression pressure applied to thechest wall side. Thus, according to the acoustic matching member 70 ofthis example, it is possible to reduce the burden on the subject at thetime of compression using the compression plate 32.

EXAMPLE 3-2

FIG. 19 shows a perspective view of an acoustic matching member 72 ofthis example, and FIG. 20 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 72 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N and a sideview when the state is viewed from the side surface of the subject.

As shown in FIGS. 19 and 20, in the acoustic matching member 72 of thisexample, the thickness of a portion in contact with the breast N changesalong the X-axis direction. Specifically, in the acoustic matchingmember 72 of this example, as shown in FIGS. 19 and 20, the shape of aportion in contact with the breast N is a protruding shape thatprotrudes toward the imaging table 31, and the thickness of a portion ofthe acoustic matching member 56 in contact with the breast N is thelargest in the central portion of the compression plate 32 in the X-axisdirection and is the smallest in the end portion of the compressionplate 32 in the X-axis direction.

The acoustic matching member 72 of this example is the same as theacoustic matching member 56 (refer to FIG. 11) of Example 1-4 of thefirst embodiment in that the shape of a portion in contact with thebreast is a protruding shape that protrudes toward the imaging table 31,but is different from the acoustic matching member 56 (refer to FIG. 11)of Example 1-4 of the first embodiment in that there is no protrudingportion corresponding to the protruding portion 56A provided in theacoustic matching member 56.

Therefore, as shown in FIGS. 19 and 20, the shape of the acousticmatching member 72 of this example when viewed from the direction of thenipple of the breast N is a protruding shape that protrudes toward theimaging table 31.

The upper acoustic matching member 80 provided on the upper surface ofthe compression plate 32 is the same as that in Example 3-1 describedabove.

As described above in Example 1-4 of the first embodiment, in general,the thickness of the breast N in the horizontal direction of the subjectincreases toward the nipple portion and decreases toward the left andright end portions of the subject. Therefore, in order to make thebreast N uniform in thickness, it is preferable to compress the nippleportion more than the left and right end portions. By forming theacoustic matching member 72 in the shape shown in FIGS. 19 and 20, it ispossible to increase the compression pressure toward the nipple portionof the breast N. As a result, it becomes easy to make the thickness ofthe breast N uniform.

EXAMPLE 3-3

FIG. 21 shows a perspective view of an acoustic matching member 74 ofthis example, and FIG. 22 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 74 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N and a sideview when the state is viewed from the side surface of the subject.

As shown in FIGS. 21 and 22, in the acoustic matching member 74 of thisexample, the thickness of a portion in contact with the breast N changesalong the Y-axis direction. Specifically, as shown in FIGS. 21 and 22,in the acoustic matching member 74 of this example, the thickness of aportion in contact with the breast N is the smallest on the chest wallside and the largest on the nipple side.

The upper acoustic matching member 80 provided on the upper surface ofthe compression plate 32 is the same as that in Example 3-1 describedabove.

As described above in Example 1-2 of the first embodiment, in general,the thickness of the breast N in the vertical direction of the subjectincreases toward the chest wall side and decreases toward the nippleside. Therefore, by forming the acoustic matching member 74 in the shapeshown in FIGS. 21 and 22, it is possible to perform compressionaccording to the shape of the breast N. As a result, it is possible toreduce the compression pressure applied to the chest wall side. Thus,according to the acoustic matching member 74 of this example, it ispossible to reduce the burden on the subject at the time of compressionusing the compression plate 32.

EXAMPLE 3-4

FIG. 23 shows a perspective view of an acoustic matching member 76 ofthis example, and FIG. 24 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 76 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N and a sideview when the state is viewed from the side surface of the subject.

As shown in FIGS. 23 and 24, in the acoustic matching member 76 of thisexample, on the chest wall side of the breast N, a protruding portion76B that protrudes in a direction away from the imaging table 31 isprovided along the side surface of the compression plate 32. In thepresent embodiment, the height of the protruding portion 76B is set to aheight corresponding to the thickness of the compression plate 32.

As shown in FIG. 24, an upper acoustic matching member 82 of thisexample is a rectangular parallelepiped having a contact surface incontact with the compression plate 32 and the protruding portion 76B ofthe acoustic matching member 76.

Since the acoustic matching member 76 of this example has the protrudingportion 76B in contact with the side surface of the compression plate32, it is sufficient to match the shape of the compression plate 32 in acase where the operator performs positioning of the acoustic matchingmember 76. Accordingly, the positioning becomes easy.

EXAMPLE 3-5

FIG. 25 shows a perspective view of an acoustic matching member 78 ofthis example, and FIG. 26 shows a front view when a state, in which thecompression plate 32 compresses the breast N with the acoustic matchingmember 78 interposed between the compression plate 32 and the breast N,is viewed from the direction of the nipple of the breast N and a sideview when the state is viewed from the side surface of the subject.

As shown in FIGS. 25 and 26, the acoustic matching member 78 of thisexample is a rectangular parallelepiped having a surface in contact withthe compression plate 32, the surface having the same area as the bottomsurface of the compression plate 32. The upper acoustic matching member80 provided on the upper surface of the compression plate 32 is the sameas that in Example 3-1 described above.

In the acoustic matching member 78 and the upper acoustic matchingmember 80, the thickness of the acoustic matching member 78 in theZ-axis direction is larger than the thickness of the upper acousticmatching member 80 in the Z-axis direction.

As described above in Example 1-1 of the first embodiment, the acousticmatching member 78 preferably has high adhesion to the breast N, and theupper acoustic matching member 80 preferably has high lubricity in orderto move the ultrasound probe 36 smoothly. Therefore, the static frictioncoefficient of the acoustic matching member 78 is larger than the staticfriction coefficient of the upper acoustic matching member 80.

For the hardness of the acoustic matching member 78, it is preferablethat, in the Y-axis direction, the hardness on the chest wall side ofthe breast N is lower than the hardness on the nipple side (in otherwords, the acoustic matching member 78 on the chest wall side of thebreast N is softer than the acoustic matching member 78 on the nippleside). In this case, since the acoustic matching member 78 tends to bedeformed on the chest wall side compared with the nipple side, theacoustic matching member 78 is likely to be deformed according to theshape of the breast N. Therefore, it is possible to reduce the burden onthe subject.

Thus, in the acoustic matching members 70 to 78 used in the medicalimaging apparatus 10 of the third embodiment, there are provided: theacoustic matching members 70 to 78 which are provided on the bottomsurface of the compression plate 32 on the breast N side in the case ofcompressing the breast N of the subject with the compression plate 32;and the upper acoustic matching members 80 and 82 which are provided onthe upper surface on the opposite side to the bottom surface of thecompression plate 32 in the case of compressing the breast N with thecompression plate 32 and whose types are different from the acousticmatching members 70 to 78.

In the present embodiment, since the type of the acoustic matchingmember provided on the bottom surface of the compression plate 32 isdifferent from the type of the upper acoustic matching member providedon the upper surface of the compression plate 32, it is possible to usean appropriate acoustic matching member and an appropriate upperacoustic matching member. Therefore, according to the presentembodiment, in the case of capturing an ultrasound image of the breast Nof the subject in a state in which the breast N is compressed by thecompression plate 32, it is possible to reduce the burden on thesubject.

In the above second and third embodiments, the cases have been describedin which the upper acoustic matching members 60, 62, 80, and 82 in theso-called gel sheet form are provided on the upper surface of thecompression plate 32. However, the upper acoustic matching memberprovided on the upper surface of the compression plate 32 is not limitedto the gel sheet form. For example, the upper acoustic matching membermay be a volatile lubricant. Thus, by using the upper acoustic matchingmember that is a gel sheet form or a volatile lubricant, it becomes easyto place the upper acoustic matching member on the upper surface of thecompression plate 32 compared with a case of using so-called echogenicjelly, which requires application and removal onto and from the uppersurface of the compression plate 32.

In each of the above embodiments, the case has been described in whichthe medical imaging apparatus 10 has a function of capturing aradiographic image and a function of capturing an ultrasound image.However, without being limited thereto, the medical imaging apparatus 10may have at least a function of capturing an ultrasound image. In ageneral mammography apparatus, in the case of capturing a radiographicimage of the breast N, the breast N of the subject is compressed by thecompression plate. On the other hand, in the case of capturing anultrasound image of the breast N using a general ultrasound imagingapparatus, the operator moves the ultrasound probe on the surface of thebreast N of the subject to perform imaging. Thus, in the case ofcapturing a radiographic image and the case of capturing an ultrasoundimage, the compression state of the breast N of the subject, the stateof imaging, and the like are different. For this reason, in the case ofcomparing both the images, it may be difficult to observe a region ofinterest. In contrast, as in the medical imaging apparatus 10 of thepresent embodiment, by providing a function of capturing a radiographicimage and a function of capturing an ultrasound image, it is possible tosuppress differences in the compression state of the breast N of thesubject, the state of imaging, and the like in the case of capturing aradiographic image and the case of capturing an ultrasound image.Therefore, according to the medical imaging apparatus 10 of the presentembodiment, the user can easily compare the radiographic image and theultrasound image with each other.

The radiation R in each of the above embodiments is not particularlylimited, and X-rays, y-rays, and the like can be applied.

The configuration, operation, and the like of the medical imagingapparatus 10 described in each of the above embodiments are examples,and it is needless to say that these can be changed according to thecircumstances within the scope not deviating from the spirit of theinvention.

For the above embodiments, the following additional notes are disclosed.

(Note 1)

An acoustic matching member group, comprising: a first acoustic matchingmember that is provided on a first surface of a compression plate on abreast side in a case of compressing the breast of a subject with thecompression plate; and a second acoustic matching member that isprovided on a second surface of the compression plate on a side oppositeto the first surface in a case of compressing the breast with thecompression plate and that is of a different type from the firstacoustic matching member.

(Note 2)

In the acoustic matching member group described in Note 1, a staticfriction coefficient of the first acoustic matching member is largerthan a static friction coefficient of the second acoustic matchingmember.

(Note 3)

In the acoustic matching member group described in Note 1 or 2, athickness of the first acoustic matching member is larger than athickness of the second acoustic matching member in a compressiondirection of the compression plate.

(Note 4)

In the acoustic matching member group described in any one of Notes 1 to3, a hardness of the first acoustic matching member on a chest wall sideof the subject is lower than a hardness of the first acoustic matchingmember on a nipple side of the subject.

(Note 5)

In the acoustic matching member group described in any one of Notes 1 to4, a surface of the first acoustic matching member in contact with thebreast of the subject has a recessed shape that is recessed toward acentral portion from an end portion in a horizontal direction of thesubject.

(Note 6)

In the acoustic matching member group described in any one of Notes 1 to4, the first acoustic matching member has a protruding shape thatprotrudes toward the imaging table.

(Note 7)

A medical imaging apparatus, comprising: the acoustic matching membergroup described in any one of Notes 1 to 6; an imaging table on whichthe breast of the subject is placed; a compression plate that compressesthe breast in contact with the acoustic matching member group; and anultrasound imaging unit that captures an ultrasound image of the breast.

(Note 8)

The medical imaging apparatus described in Note 7, further comprising: aradiographic imaging unit that captures a radiographic image of thebreast.

What is claimed is:
 1. An acoustic matching member group, comprising: alower acoustic matching member configured to be disposed between abreast placed on an imaging table and a compression plate disposedopposite to the imaging table; and an upper acoustic matching memberprovided on a surface of the compression plate opposite to a surfacefacing the imaging table, configured for compressing the breast of thesubject in contact with the compression plate, wherein a static frictioncoefficient of the lower acoustic matching member is larger than astatic friction coefficient of the upper acoustic matching member. 2.The acoustic matching member group according to claim 1, wherein athickness of the lower acoustic matching member on the chest wall sideof the subject is smaller than that in the end portion on the deepestside.
 3. The acoustic matching member group according to claim 1,wherein a surface configured to be in contact with the breast of thesubject has a recessed shape that is recessed toward a central portionfrom an end portion in a horizontal direction of the subject.
 4. Theacoustic matching member group according to claim 1, wherein the loweracoustic matching member has a protruding shape that protrudes towardthe imaging table.
 5. The acoustic matching member group according toclaim 1, wherein the lower acoustic matching member is configured tohave a higher hardness than a hardness set in advance as a hardness ofthe breast.
 6. The acoustic matching member group according to claim 1,wherein the lower acoustic matching member is formed of a gel material.7. The acoustic matching member group according to claim 1, wherein theupper acoustic matching member is formed of a gel material.
 8. Theacoustic matching member group according to claim 1, wherein the upperacoustic matching member is formed of a volatile lubricant.
 9. Theacoustic matching member group according to claim 1, wherein a thicknessof the lower acoustic matching member in a compression direction of thecompression plate is larger than a thickness of the upper acousticmatching member.
 10. A medical imaging apparatus, comprising: theacoustic matching member group according to claim 1; an imaging tableconfigured for placement of the breast of the subject; a compressionplate configured such that it compresses the breast in contact with thelower acoustic matching member; an ultrasound probe configured to scanthe breast of the subject with ultrasound waves to acquire an ultrasoundimage of the breast; and a processor that is configured to control theultrasound probe to capture an ultrasound image of the breast.
 11. Amedical imaging apparatus, comprising: the acoustic matching membergroup according to claim 1; an imaging table configured for placement ofthe breast of the subject; a compression plate that compresses thebreast in contact with the acoustic matching member group; an ultrasoundprobe configured to scan the breast of the subject with ultrasound wavesto acquire an ultrasound image of the breast; and a processor that isconfigured to control the ultrasound probe to capture an ultrasoundimage of the breast.
 12. The medical imaging apparatus according toclaim 10, further comprising: a radiation emitter that emits radiation;and a radiation detector configured to detect radiation transmittedthrough the breast; wherein the processor is further configured tocontrol the radiation emitter and the radiation detector to capture aradiographic image of the breast.